# What is dilution in physics

## Understanding Physics 2, Student Book

72 3  Workbook, pages 42–43 Origin and propagation of sound 1. How is sound created? Tinting glasses (Fig.72.1) E1 Fill a thin-walled wine glass half full with water. Moisten your index finger a little and slide it along the edge of the glass. If you make the glass vibrate, a tone will sound. Change the pitch by changing the amount of water. Splashing sound (Fig.72.2) E1 Strike a tuning fork. You can hear their sound when you hold them against a wooden plate, for example (Fig. 6.3). If you dip the struck tuning fork into the water, it splatters away on all sides. When an elastic body swings back and forth very quickly, sound is created. These bodies are called sound sources. You can see the vibrations on the strings of a guitar. If you hold your fingertips against the larynx while speaking, you will feel the vibrating of the vocal cords (Fig. 72.3). 2. How does the sound propagate? Can drums (Fig.72.5) E1 Remove the bottom and lid from two cans and cover an opening with a rubber membrane, eg a rubber glove. Line up the cans with the openings facing each other. Hang a ping pong ball by the second can and hit the eardrum of the first can drum. The ping pong ball moves when you hit the first can. If you hit the first bottom of the can at V3, the air behind it will be compressed. As a result of collisions with the neighboring air particles, the zone of the compressed air moves further and further away from the sound source - a pressure wave runs through the air (Fig. 72.4). If the pressure wave hits the bottom of the second box, this is also made to vibrate and pushes the table tennis ball away. V1 72.1 Sounding glasses V2 72.2 Splashing sound Sound is created when an elastic body vibrates rapidly. M 72.3 The vocal cords in the human larynx V3 72.5 Can drums A sound source creates compression and thinning of the air, which spread as sound waves in all directions. Sound cannot propagate without air. M 72.6 Without air you can no longer hear the ringing. Compression Dilution Compression 1 2 3 4 5 Dilution 72.4 Sound waves are compressions and dilutions of air. For testing purposes only - property of the publisher öbv

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